Upon cutting a semiconductor wafer or multilayer capacitor sheet into pieces of a predetermined size, conventionally known as a pressure-sensitive adhesive sheet for causing it to adhere to the wafer or sheet (adherend) and facilitating release and collection of cut pieces such as cut chips is a thermal-releasable pressure-sensitive adhesive sheet having a blowing-agent-containing pressure-sensitive adhesive layer disposed on a high elastic film or sheet base material such as plastic (JP-B-50-13878, JP-B-51-24534, JP-A-56-61468, JP-A-56-61469, JP-A-60-252681, etc.). This thermal-releasable pressure-sensitive adhesive sheet is aimed at both retention of adhesion enough for withstanding cutting of the adherend and easy release and collection of the cut pieces. Described specifically, this sheet is caused to adhere to the adherend with high adhesion, but upon collection of the cut pieces, the cut pieces can be released easily, because the expandable pressure-sensitive adhesive layer containing thermo-expandable microspheres foams or expands by heating to have a roughened surface, leading to lowering or loss of adhesion due to a decrease in the adhesion area with the adherend.
Since the adhesive layer of the above-described thermal-releasable pressure-sensitive adhesive sheet is soft and, due to thermo-expandable microspheres contained in the layer, is thick, problems such as winding up of the adhesive by a cutting blade or chipping associated with vibration of the pressure-sensitive adhesive layer occur upon cutting of the adherend. Thinning of the pressure-sensitive adhesive layer is effective for overcoming the above-described problems. If the layer is made thinner than the diameter of the thermo-expandable microspheres, however, these microspheres protrude from the surface of the layer and impair its smoothness, making it impossible to exhibit adhesion enough to retain the adherend. Accordingly, the thermal-releasable pressure-sensitive adhesive layer cannot be thinned without limitation and the above-described problem cannot always be overcome by thinning.
In addition, the conventional thermal-releasable pressure-sensitive adhesive sheet is sometimes unsuited for applications requiring low contamination such as semiconductor, because minute cohesion failure is induced by deformation of the thermo-expandable microspheres at the interface of the pressure-sensitive adhesive layer and the adherend happens to be contaminated by the adhesive transferred thereto.